Impellers

Capt jgw · Jan 2, 2015

A lot of sailors only change their impellers "when they need it". The trick is, how do you know when they need it? When the engine over heats? They should probably be changed at least once a season, more if your season is long. An impeller can look just fine right up to the point when the vanes break off, so it's best to be ahead of it.
There should also be some type of strainer on the intake to keep the junk put of the exchanger. Where I'm at we have a problem with water milfoil which gets chopped up by the prop and will clog an internal strainer quickly. I added an external clam shell strainer with the slots facing aft and have not had any more problems.

Terry Cox · Jan 2, 2015

FWIW, our 1991 Hunter that we purchased in 2002 has a 4JH2-TE with 1,700 hours on the engine (647 hours when we took possession) and an Onan Genset with 450 hours (280 hours when we took possession). I replaced the original impeller on the Genset for the first time last year; it was due, but still working with all vanes intact and some cracking in the rubber material. I have yet to check the condition of or replace the main engine impeller. The PO had replaced it at least once. I suppose I'll replace it this coming season with the spare I have on board.

artboas · Jan 6, 2015

Here's the problem...

seadaddler said:
Well I went to check my Yanmar recently and checked my 2 belts and changed the water pump belt after finding a kind of cut on it and while checking the impeller found one of the vanes missing and after just coming back from cruising
for about 3 weeks with much motoring and will check everything more before
going on one of our longer cruises and the motor did run great.
After finding the vane gone i decided to take the heat exchanger on my 2007
3YM30 and found 2 vanes in the front part of the heat exchanger and also some
sea grass but all good now.
Nick

I would normally pull the impeller every fall just to check it.
But, on the 49 it is a 2 hour job (minimum)
I'm sure that the 49 & 50aC owners are well aware of this issue.
As mentioned, I've come up with a solution to this problem which I'll be implementing in the Spring.
I am confident that my solution will permit impeller change in 15 minutes.
I'll have photos once it's finalized

ELMAX · Jan 14, 2015

I would also recommend, to control the zinc sacrificial, I decided to do a restore of the engine, and I also replaced the exhaust smoke but my water and very old. The impeller to change every year, if it does not turn sea water, before the engine warms up, it burns the muffler, because it is not soft dim the temperature of the exhaust smoke, and there is the danger of fire.

ELMAX · Jan 14, 2015

ELMAX said:
I would also recommend, to control the zinc sacrificial, I decided to do a restore of the engine, and I also replaced the exhaust smoke but my water and very old. The impeller to change every year, if it does not turn sea water, before the engine warms up, it burns the muffler, because it is not soft dim the temperature of the exhaust smoke, and there is the danger of fire.

For this reason it would be better to put a temperature sensor on the muffler with an alarm, if the impeller is broken muffler burns before the engine warms up, but if part of an alarm, and more secure.

ELMAX · Jan 20, 2015

Sorry for my English I think this is best to understand me.
The Council controls the anti corrosive zinc, i made the restoration of the engine, and I found the broken elbow mixing. The impeller to change every year, but it depends on how many hours the engine are made, if the impeller breaks, before damaging the engine burns the muffler, exhaust smoke is not cooled by sea water, the danger is a fire.
To find out if the impeller broke, i put a temperature sensor 85 degrees with a alarm on the muffler

Ralph Johnstone · Jan 20, 2015

A Faster Indicator ..................

ELMAX said:
To find out if the impeller broke, i put a temperature sensor 85 degrees with a alarm on the muffler

.................. would be a flow switch. This gives you an alarm as soom as cooling water flow decreases.

uncledom · Jan 20, 2015

Ralph Johnstone said:
.................. would be a flow switch. This gives you an alarm as soom as cooling water flow decreases.

WOW. You could eat lunch in that engine compartment! Nice Ralph
Who makes that flow switch?

Ralph Johnstone · Jan 21, 2015

uncledom said:
WOW. You could eat lunch in that engine compartment! Nice Ralph
Who makes that flow switch?

Check the attached literature for flow switch specs. I believe it was about $70.00 when I bought it 8 years back.

As for the engine compartment ................ it has to be that clean. That's where I hide my lunch. Bloody crew would have it eaten within minutes if I left it lying around

.

ELMAX · Jan 21, 2015

Congratulations, beautiful engine.

excellent idea flowmeter.

HMT2 · Jan 21, 2015

Ralph Johnstone said:
Check the attached literature for flow switch specs. I believe it was about $70.00 when I bought it 8 years back. As for the engine compartment ................ it has to be that clean. That's where I hide my lunch. Bloody crew would have it eaten within minutes if I left it lying around .

Ralph, that is a brilliant idea, flow switch. I assume it is attached to some kind of alarm? I did not see any literature attached, I would be interested in doing this to my Yanmar 2gm. What kind of switch did you use?

Ralph Johnstone · Jan 21, 2015

No Attachments ? ? ? ? ...................

HMT2 said:
I did not see any literature attached, I would be interested in doing this to my Yanmar 2gm. What kind of switch did you use?

Had another enquiry complaining about not being able to see the .PDF attachment so maybe it's common problem. If you can't see the previous .PDF attachments, please see this site:

http://aqualarm.net/cooling-water-flow-c-2/

for Aquaflow products.

I see they've changed their technology from a magnetic slug on a guide rail being moved by the water flow against a spring ........... to a flow paddle which has a pivot point. This is the same as used in industrial flow detectors so if anything, it's better than what I have and it's $5.00 bloody dollars less than what I paid eight years ago

.

The alarm can be wired through the same alarm as the low oil pressure alarm. I went a little more exotic and wired it through a different sounding alarm (physically the same alarm but on a different audible output) just so I can audibly check both alarms on engine startup. They both sound until I have both oil pressure and water flow.

With their expanded selection, for a Yanmar 2GM20F, you'd want the 10235 Cooling Water Flow Detector.

I hope this helps.

Don Crowther · Jan 21, 2015

Ralph
I was able to read it with no problems. So I think all is good on your end.

HMT2 · Jan 21, 2015

Ralph Johnstone said:
Had another enquiry complaining about not being able to see the .PDF attachment so maybe it's common problem. If you can't see the previous .PDF attachments, please see this site: http://aqualarm.net/cooling-water-flow-c-2/ for Aquaflow products. I see they've changed their technology from a magnetic slug on a guide rail being moved by the water flow against a spring ........... to a flow paddle which has a pivot point. This is the same as used in industrial flow detectors so if anything, it's better than what I have and it's $5.00 bloody dollars less than what I paid eight years ago . The alarm can be wired through the same alarm as the low oil pressure alarm. I went a little more exotic and wired it through a different sounding alarm (physically the same alarm but on a different audible output) just so I can audibly check both alarms on engine startup. They both sound until I have both oil pressure and water flow. With their expanded selection, for a Yanmar 2GM20F, you'd want the 10235 Cooling Water Flow Detector. I hope this helps.

Thank you Ralph. Mine is a straight 2gm with raw sea water cooling, there is no fresh water component. Would your recommendation be the same? Also, I am viewing this from an iPad and SBO app not a computer, perhaps that's why I can't see the attachment. I will check from my computer later and see.

uncledom · Jan 21, 2015

Thanks for the link Ralph

artboas · Jan 21, 2015

Here's what I did

Ralph Johnstone said:
Had another enquiry complaining about not being able to see the .PDF attachment so maybe it's common problem. If you can't see the previous .PDF attachments, please see this site:

http://aqualarm.net/cooling-water-flow-c-2/

for Aquaflow products.

I see they've changed their technology from a magnetic slug on a guide rail being moved by the water flow against a spring ........... to a flow paddle which has a pivot point. This is the same as used in industrial flow detectors so if anything, it's better than what I have and it's $5.00 bloody dollars less than what I paid eight years ago .

The alarm can be wired through the same alarm as the low oil pressure alarm. I went a little more exotic and wired it through a different sounding alarm (physically the same alarm but on a different audible output) just so I can audibly check both alarms on engine startup. They both sound until I have both oil pressure and water flow.

With their expanded selection, for a Yanmar 2GM20F, you'd want the 10235 Cooling Water Flow Detector.

I hope this helps.

Firstly, your choice of Aqualarm was spot on.
An excellent unit, and real cheap.
I put one on my genset, as well as engine.
But, I went a little more complex.
I wired both systems so that the engine & genset will automatically shut down if the intake sucks in a bag, etc.
There is a selector switch which bypasses the auto-shutdown, so it can be an audible alert only.
Here's why I did this:
On my Genset, hunter put in a water / gas separator.

You can't hear the genset running if you're in the cockpit.,,its that quiet.
So, that's the good news.
The bad news is that you just wont know if your water intake becomes blocked, as the water exhausts below waterline.

I've tested both genset & engine, and they shut down within 3 seconds of an intake blockage.
I leave the engine on bypass mode, where it's just an alarm sounding if a blockage occurs, but I do have the auto shutdown available if I want it enabled.

Ralph Johnstone · Jan 22, 2015

Flow Rate Requirement

HMT2 said:
Mine is a straight 2gm with raw sea water cooling, there is no fresh water component. Would your recommendation be the same?

Not familiar with how much sea water your engine would pass.

Best to try a test measuring the raw water pump intake from a bucket and compare to Aqualarm's required 3-4 gpm flow rate for their 10235 detector.
.

artboas · Jan 22, 2015

It's adjustable

Ralph Johnstone said:
Not familiar with how much sea water your engine would pass.

Best to try a test measuring the raw water pump intake from a bucket and compare to Aqualarm's required 3-4 gpm flow rate for their 10235 detector.
.

The sensor is adjustable.
All you need to do is as follows:
Run engine
Start adjusting sensor until alarm sounds
Then back off on the adjustment.
Super-easy.
The adjustment isn't super-critical. There is a very large variation in intake pressure between open flow & restricted.
Highly reccomend the Aqualarm sensor.